Metal-oxide-semiconductor field effect transistors (MOSFETs) are semiconductor devices commonly employed for switching power on and off. A MOSFET includes a source region, a drain region, and a channel region extending between the source and drain regions. The channel region is separated from a gate electrode by a thin dielectric layer, so that a voltage applied to the gate electrode can control whether a conductive channel forms between the source and the drain regions. When the conductive channel is present, the MOSFET enables current to pass through the device, subject to an on-state resistance. When the conductive channel is absent, the device blocks current flow until such time as a breakdown voltage is reached.
It is desirable to make on-state resistance as small as possible while making the breakdown voltage as high as possible, but traditionally these parameters have had to be traded-off against each other. This trade-off constraint has been relaxed (though not eliminated) through the use of so-called “super-junction” devices. Such devices employ adjacent layers of oppositely-doped semiconductor to provide charge carriers for on-state conduction and depletion regions (equivalent to carrier-less “intrinsic” semiconductor material) for off-state current blocking.
Nevertheless, existing super-junction construction technologies suffer from a number of shortcomings, including limited device pitch (causing semiconductor volume to be wasted) and termination difficulty. The former shortcoming requires devices to be larger than necessary. The later shortcoming unnecessarily limits device reliability and yield.